1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * stacktrace.c : stacktracing APIs needed by rest of kernel 4 * (wrappers over ARC dwarf based unwinder) 5 * 6 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) 7 * 8 * vineetg: aug 2009 9 * -Implemented CONFIG_STACKTRACE APIs, primarily save_stack_trace_tsk( ) 10 * for displaying task's kernel mode call stack in /proc/<pid>/stack 11 * -Iterator based approach to have single copy of unwinding core and APIs 12 * needing unwinding, implement the logic in iterator regarding: 13 * = which frame onwards to start capture 14 * = which frame to stop capturing (wchan) 15 * = specifics of data structs where trace is saved(CONFIG_STACKTRACE etc) 16 * 17 * vineetg: March 2009 18 * -Implemented correct versions of thread_saved_pc() and get_wchan() 19 * 20 * rajeshwarr: 2008 21 * -Initial implementation 22 */ 23 24 #include <linux/ptrace.h> 25 #include <linux/export.h> 26 #include <linux/stacktrace.h> 27 #include <linux/kallsyms.h> 28 #include <linux/sched/debug.h> 29 30 #include <asm/arcregs.h> 31 #include <asm/unwind.h> 32 #include <asm/switch_to.h> 33 34 /*------------------------------------------------------------------------- 35 * Unwinder Iterator 36 *------------------------------------------------------------------------- 37 */ 38 39 #ifdef CONFIG_ARC_DW2_UNWIND 40 41 static void seed_unwind_frame_info(struct task_struct *tsk, 42 struct pt_regs *regs, 43 struct unwind_frame_info *frame_info) 44 { 45 /* 46 * synchronous unwinding (e.g. dump_stack) 47 * - uses current values of SP and friends 48 */ 49 if (tsk == NULL && regs == NULL) { 50 unsigned long fp, sp, blink, ret; 51 frame_info->task = current; 52 53 __asm__ __volatile__( 54 "mov %0,r27\n\t" 55 "mov %1,r28\n\t" 56 "mov %2,r31\n\t" 57 "mov %3,r63\n\t" 58 : "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret) 59 ); 60 61 frame_info->regs.r27 = fp; 62 frame_info->regs.r28 = sp; 63 frame_info->regs.r31 = blink; 64 frame_info->regs.r63 = ret; 65 frame_info->call_frame = 0; 66 } else if (regs == NULL) { 67 /* 68 * Asynchronous unwinding of sleeping task 69 * - Gets SP etc from task's pt_regs (saved bottom of kernel 70 * mode stack of task) 71 */ 72 73 frame_info->task = tsk; 74 75 frame_info->regs.r27 = TSK_K_FP(tsk); 76 frame_info->regs.r28 = TSK_K_ESP(tsk); 77 frame_info->regs.r31 = TSK_K_BLINK(tsk); 78 frame_info->regs.r63 = (unsigned int)__switch_to; 79 80 /* In the prologue of __switch_to, first FP is saved on stack 81 * and then SP is copied to FP. Dwarf assumes cfa as FP based 82 * but we didn't save FP. The value retrieved above is FP's 83 * state in previous frame. 84 * As a work around for this, we unwind from __switch_to start 85 * and adjust SP accordingly. The other limitation is that 86 * __switch_to macro is dwarf rules are not generated for inline 87 * assembly code 88 */ 89 frame_info->regs.r27 = 0; 90 frame_info->regs.r28 += 60; 91 frame_info->call_frame = 0; 92 93 } else { 94 /* 95 * Asynchronous unwinding of intr/exception 96 * - Just uses the pt_regs passed 97 */ 98 frame_info->task = tsk; 99 100 frame_info->regs.r27 = regs->fp; 101 frame_info->regs.r28 = regs->sp; 102 frame_info->regs.r31 = regs->blink; 103 frame_info->regs.r63 = regs->ret; 104 frame_info->call_frame = 0; 105 } 106 } 107 108 #endif 109 110 notrace noinline unsigned int 111 arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs, 112 int (*consumer_fn) (unsigned int, void *), void *arg) 113 { 114 #ifdef CONFIG_ARC_DW2_UNWIND 115 int ret = 0; 116 unsigned int address; 117 struct unwind_frame_info frame_info; 118 119 seed_unwind_frame_info(tsk, regs, &frame_info); 120 121 while (1) { 122 address = UNW_PC(&frame_info); 123 124 if (!address || !__kernel_text_address(address)) 125 break; 126 127 if (consumer_fn(address, arg) == -1) 128 break; 129 130 ret = arc_unwind(&frame_info); 131 if (ret) 132 break; 133 134 frame_info.regs.r63 = frame_info.regs.r31; 135 } 136 137 return address; /* return the last address it saw */ 138 #else 139 /* On ARC, only Dward based unwinder works. fp based backtracing is 140 * not possible (-fno-omit-frame-pointer) because of the way function 141 * prelogue is setup (callee regs saved and then fp set and not other 142 * way around 143 */ 144 pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n"); 145 return 0; 146 147 #endif 148 } 149 150 /*------------------------------------------------------------------------- 151 * callbacks called by unwinder iterator to implement kernel APIs 152 * 153 * The callback can return -1 to force the iterator to stop, which by default 154 * keeps going till the bottom-most frame. 155 *------------------------------------------------------------------------- 156 */ 157 158 /* Call-back which plugs into unwinding core to dump the stack in 159 * case of panic/OOPs/BUG etc 160 */ 161 static int __print_sym(unsigned int address, void *unused) 162 { 163 printk(" %pS\n", (void *)address); 164 return 0; 165 } 166 167 #ifdef CONFIG_STACKTRACE 168 169 /* Call-back which plugs into unwinding core to capture the 170 * traces needed by kernel on /proc/<pid>/stack 171 */ 172 static int __collect_all(unsigned int address, void *arg) 173 { 174 struct stack_trace *trace = arg; 175 176 if (trace->skip > 0) 177 trace->skip--; 178 else 179 trace->entries[trace->nr_entries++] = address; 180 181 if (trace->nr_entries >= trace->max_entries) 182 return -1; 183 184 return 0; 185 } 186 187 static int __collect_all_but_sched(unsigned int address, void *arg) 188 { 189 struct stack_trace *trace = arg; 190 191 if (in_sched_functions(address)) 192 return 0; 193 194 if (trace->skip > 0) 195 trace->skip--; 196 else 197 trace->entries[trace->nr_entries++] = address; 198 199 if (trace->nr_entries >= trace->max_entries) 200 return -1; 201 202 return 0; 203 } 204 205 #endif 206 207 static int __get_first_nonsched(unsigned int address, void *unused) 208 { 209 if (in_sched_functions(address)) 210 return 0; 211 212 return -1; 213 } 214 215 /*------------------------------------------------------------------------- 216 * APIs expected by various kernel sub-systems 217 *------------------------------------------------------------------------- 218 */ 219 220 noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs) 221 { 222 pr_info("\nStack Trace:\n"); 223 arc_unwind_core(tsk, regs, __print_sym, NULL); 224 } 225 EXPORT_SYMBOL(show_stacktrace); 226 227 /* Expected by sched Code */ 228 void show_stack(struct task_struct *tsk, unsigned long *sp) 229 { 230 show_stacktrace(tsk, NULL); 231 } 232 233 /* Another API expected by schedular, shows up in "ps" as Wait Channel 234 * Of course just returning schedule( ) would be pointless so unwind until 235 * the function is not in schedular code 236 */ 237 unsigned int get_wchan(struct task_struct *tsk) 238 { 239 return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL); 240 } 241 242 #ifdef CONFIG_STACKTRACE 243 244 /* 245 * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP. 246 * A typical use is when /proc/<pid>/stack is queried by userland 247 */ 248 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) 249 { 250 /* Assumes @tsk is sleeping so unwinds from __switch_to */ 251 arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace); 252 } 253 254 void save_stack_trace(struct stack_trace *trace) 255 { 256 /* Pass NULL for task so it unwinds the current call frame */ 257 arc_unwind_core(NULL, NULL, __collect_all, trace); 258 } 259 EXPORT_SYMBOL_GPL(save_stack_trace); 260 #endif 261